4.2 Carbohydrates

activity

Task Read the passage in the textbook. Complete the concept map.

After that, in your group, discuss about following topics.

Group1:types of carbohydrates

Group2:reducing and nonreducing sugar

Group3:process of formation and breakdown of disaccharides and polysaccharides

You have 10 minutes to complete the tasks.

Carbohydrates

• An important source of energy that can be used by cell

• Contain C, H and O

• Ratio H:O = 2:1

Types of Carbohydrate

s

disaccharides

monosaccharides

polysaccharides

Monosaccharides

• Monomer of carbohydrates

• Simplest type of carbohydrates

• Known as simple sugar = main source of energy.

• Combine with protein = glycoprotein

• Combine with lipid = glycolipid

Monosaccharides

• Examples – glucose, fructose and galactose

• Glucose – plants and fruit

• Fructose – sweet fruits and honey

• Galactose - milk

Disaccharides

• Formed when 2 monosaccharides combine through condensation process.

• Condensation = process which involves the removal of a water molecule when a bond is formed between 2 molecules of monosaccharides.

• Examples – sucrose, lactose and maltose

Disaccharides

Glucose + glucose

Glucose + fructose

Sucrose + water

Glucose + galactose

Maltose + water

Lactose + water

Condensation Hydrolysis

Polysaccharides

• Polymers formed by the condensation of glucose monomers.

• Insoluble in water due to large molecular size

• Do not taste sweet and do not crystallize.

• Examples – starch, glycogen and cellulose.

Polysaccharides

• Starch – wheat, rice, potatoes, bread and corn.

• Cellulose – plant cell wall

• Glycogen – animal (liver & muscle cell) and yeast.

• Glycogen = animal starch

• Glycogen is highly branched

Polysaccharides

Polysaccharides

• Can be broken down into smaller molecules through hydrolysis by adding diluted acid or through enzymatic reaction.

Polysaccharides + water

Monosaccharides

activity

Differentiating between reducing and non-reducing sugars.

Objective

To investigate the properties of reducing and non-reducing sugar

Hypothesis

Reducing sugar will reduce the color of Benedict’s solution from blue to red brick precipitate

Variables

1.Manipulative = types of sugar

2. Responding = changes in the color of Benedict ‘s solution

3. Constant = volume of sugar, volume of Benedict’s solution.

Procedures

Observation

Solution

Observation Inference

Glucose Blue red brick

precipitate

Glucose reduces CuSO4 to CuO

Sucrose Remain blue Sucrose do not reduces CuSO4 to CuO

Sucrose + HCl

Blue red brick

precipitate

Sucrose is hydrolyzed into glucose and fructose. Both of them can reduce CuSO4 to CuO

Question

1. What information can you draw from the result that you have obtained?

2. What is the effect of dilute HCl acid on sucrose?

3. Classify the glucose and sucrose sugars according to their properties based on the experiment?

Discussion

1.When glucose is heated with Benedict’s solution, it reduces the blue copper(II) sulphate in the Benedict’s solution to form a precipitate of copper(I)oxide.

Therefore, glucose is a reducing sugar.

Discussion

Sucrose do not reduce the Benedict solution upon heating.

Therefore, sucrose is a non-reducing sugar.

Discussion

2.When heating sucrose with dilute HCl, it is hydrolysed into glucose and fructose.

When the solution containing glucose and fructose is boiled with Benedict’s solution, it produces red brick precipitate.

Discussion

3. Glucose is a reducing sugar.

Sucrose ia a non-reducing sugar.

Conclusion

• Glucose is a reducing sugar.

• Sucrose ia a non-reducing sugar.

Benedict’s test

Increasing amount of reducing sugar

green

orange

Red brick precipitate

All monosaccharides are reducing sugar

Lactose and maltose are reducing sugar but sucrose are non-reducing

sugar

activity

We are the millionaire

Rules

1. Makes sure you have the answer before you raised your hand.

2. Your turn will be given to other group if you are taking time to give your answer.

3. If you give the correct answer, you given a chance to draw a letter stating the value your group have win.

4. For the wrong answer, you will lose rm1000

1

State 3 types of carbohydrates

Monosaccharides, disaccharides and

polysaccharides

2

Gives 3 groups of monosaccharides sugar

Glucose,Fructose and

Galactose

3

Galactose can be found in ___________milk

4

Disaccharides can be broken down by the process of ________hydrolysis

5

State 3 group of polysaccharides

StarchGlycogenCellulose

6

What is condensation?

Process which involves the removal of a water molecule

when a bond is formed between 2 monosaccharides

7

What is the monomer of polysaccharides?

glucose

8

What is the effect of adding dilute HCl acid into sucrose solution?

Sucrose is broken down into glucose and fructose.

Sucrose is hydrolysed.

9

Name all the reducing sugars

GlucoseFructose

GalactoseMaltoseLactose

10

Monomers of maltose is ____________glucose

11

The presence of reducing sugar in a solution can be test using Benedict’ solution. What is the observation if the reducing sugar is present in the solution?

Blue color change to red brick precipitate

assessment

Question

1. List all 3 elements in the carbohydrates.

2. List all 3 types of carbohydrates

3. Explain the formation and breakdown of sucrose, lactose and maltose

4. Explain the formation and breakdown of polysaccharides

conclusion